A new threat assessment measure for collision avoidance systems

Collision avoidance systems (CAS) are an emerging automotive safety technology that assists drivers in avoiding collisions. They monitor the dynamic traffic and vehicle information in real time and assess the current threat level to decide if warnings should be issued to the driver or automatic braking is needed to avoid collisions. Several measures have previously been defined for threat assessment with various warning and overriding algorithms proposed. A new threat assessment measure, time-to-last-second-braking (T_lsb) is proposed in this paper and its advantages over previous measures are discussed. It directly quantifies the danger or threat level of the current dynamic situation objectively as well as assesses the urgency level for the required evasive action, e.g., braking. It is in agreement with human natural judgment of the urgency and severity of threats. Furthermore, new warning and overriding criteria are proposed based on the new T_lsb measure, providing more appropriate warning and more effective override timing